Single lever control mechanism for aircraft engine



April 3, 1956 s. MAcHLANsKl SINGLE LEVER CONTROL MECHANISM FOR AIRCRAFT ENGINE 8 Sheets-Sheet l Filed Sept. 20, 1950 L. mom n .Sa So JNVENToR.

LANSK/ S/GMUND April 3, 1956 s. MACHLANSKI 2,740,255

SINGLE LEVER CONTROL MECHANISM FOR AIRCRAFT ENGINE Filed Sept. 20, 1950 8 Sheets-Sheet 2 m w m. m M W m 5 April 3, 1956 s. MAcHLANsKl SINGLE LEVER CONTROL MECHANISM FOR AIRCRAFT ENGINE Filed sept. zo, 195o 8 Sheets-Sheet 5 aD OJJ Om mmk INVENTOR. S/GMUND MACHL ANSK/ /9 WOR/VE Y mbx 5 Bodom nav Fw m NW Om U ammo wwe/Al un Q Nm\M wim .Ud

April 3, 1956 s. MAcHLANsKi 2,740,255

SINGLE LEVER CONTROL MECHANISM FOR AIRCRAFT ENGINE Filed Sept. 20, 1950 8 Sheets-Sheet 4 FIG. 4

STARTER CONTROL AND FUEL REGULATOR 2 VAR/ABLE DIS PfC/YIENT M INVENTOR.

S/GMUND MACHLANSK/ April 3, 1956 s. MAcI-ILANSKI 2,740,255

SINGLE LEVER CONTROL MECHANISM FOR AIRCRAFT ENGINE med sept. 2o, 195o a sheets-sheet 5 FIG. 6

START MIN. MAX. CUTOFF GSHD POWER PowER AJ onpv@ Fg /G I I Q- C 359 --5--- DJ FLIc-I-IT CRUISE TAXI l TAXI REVERSE C FoRwARD GROUND OPERATION INVENTOR.

S/GMUND MACHLANSK/ Bmg HTTORNEV April 3, 1956 s. MAcHLANsKl SINGLE LEVER CONTROL MECHANISM FOR AIRCRAFT ENGINE Filed Sept. 20, 1950 8 Sheets-Sheet 6 INVENToR. S/GMUND MCHLANSK/ BY /97T0/e/VEY April 3, 1956 s. MAcHLANsKl 2,740,255

SINGLE LEVER CONTROL MECHANISM FOR AIRCRAFT ENGINE Filed Sept. 20, 1950 a sheets-sheet 'I INVEN TOR.

April 3, 1956 s. MAcHLANsKl SINGLE LEVER CONTROL MECHANISM FOR AIRCRAFT ENGINE Filed Sepl.. 20, 1950 8 Sheets-Sheet 8 United States Patent SINGLE LEVER CUNTRQL MECHANISM FOR AIRCRAFT ENGINE Sigmund Machlanski, Hackensack, N. J., assignorto Bendix Aviation Corporation, Teterboro, N. Si., a corporation of Delaware yApplication September. 20, 19S0,.Serial No. 185,828

9 Claims. (Cl. titl-39.23)

The present application relates to improvements 4in a control system for a turbine driven aircraft engine and ly operable control to determine the operating condition v of the control system.

`Another object of the invention is to provide a novel `manually operable single control for effecting simultaneously the pitch of an aircraft propeller and the temperature of combustion gases for driving the propeller through a turbine and which subject matter has been-further disclosed and claimed in application Serial No. 268,- 304,` tiled January 25, 1952, by Sigmund Machlansk as a division of the present application.

Another object of the invention is to provide a manually operable mechanism having a single control lever to effect through a system of switches an automatic starting and power control system for an aircraft engine and which subject matter has been further' disclosed -and claimed in application Serial No. 268,303,1iled January 25, 1952, by Sigmund Machlanski as a division of the present application.

Another object of the invention is to provide `novel adjustable stop means for limiting the extent of adjustmentrof the control lever to a safe operating range and which subject matter has been further disclosed and claimed in the aforesaid divisional application Serial No. 268,303. Another object of the invention is to provide a novel servo operated stop ladjustably positioned by a control computer as a function of several variables affecting safe maximum engine temperature and power conditions.

`Another object of the invention is to provide approtective device to compute continuously maximuinsafe engine temperature and power conditions and inwhich said protective device is arranged to position a mechanical stop so as to limit the extent of permissible adjustment of a master engine temperature and engine power `coritrol to within the safe range.

The above and other objects and features of the invention will appear more fully hereinafter from a consideration of the following description taken in connection with the accompanying drawings wherein oneY embodiment of the invention is illustrated by way of example.

In the drawings:

Figure 1 is a diagrammatic view showing a temperature responsive fuel control system for the automatic starting of a turbine driven engine in which there is provided a speed responsive mechanism for' effecting the necessary accessory functions in the starting operations.

Figure 2 is a diagrammatic view showing the switching 2,740,255 Patented Apr. 3, 1956 system foi-the automatic starter control operated by the speed responsive mechanism of Figure 1.

Figure3 is a diagrammatic view showing the fuel con- :trol system'for normal ground and flight operation. Figure 4-,is a diagrammatic viewof an aircraft engine or gas turbine with which the systems shown in Figures l 2 and 3 aredesigned for use.

FigureJS is a perspective view of the novel pilot control for the system. Y Figure 6 isadiagrammatic view showing thek schedule `of operation. of the pilot control.

Figure 7 isran exploded view of the operating mecha- `nism for the pilot control of Figure 5.

Figure 8is an enlarged fragmentary view illustrating the spring toggle action of the shift plate of Figure 7.

Figure `9` isadiagrammatic view showing the propeller pitch governor control circuit.

-Figure 10 is a diagrammatic view showing the stop computer for .the control system.

Figure` 11 is a diagrammatic view showing a modification of the system of Figure 4 in which there is shown a fuel pump` of the variable displacement type controlled `bfya suitable motor.

Referring to the drawing of Figure 4, there is indicated by the numeral 2 an aircraft of a type with which -the subject invention is designed for.. use. The aircraft in llightmoves toward theleft as viewed in'Figure'4 so that air isrammcd into an intake.5. `The ramair` is in turn compressed bya blower or .compressor1 8 and owsfthrough a. condui't`l10 ,intoa combustion chamberflZ. `Fuel atfa controlled rate is fed through lines 16 into the combustion chamber 12.

.The products of combustion `ilow out through a nozzle ,18, to .drive a turbine 20 whichdrives the compressor 8 and a propellerZl through a shaft 22. The exhaust exits .throughpassage'23- Gearing 24 and a shaft 26 connects the shaft 22 with a ilyball speed governor 27 of Figures l and 3 ofthe automatic starter control and fuelrregulator 28 hereinafterexplained.

` The pitch of the blades ofthe propeller V211mayv be varied byarsuitable mechanism. 29 under control of the pilot as hereinafter explained. j

Temperature responsivedevicet) sensitive to the temperatureofthe air at the intake 5 is operably connected through a conduit 31 to, the fuel regulator for purposes hereinaftcrpexplained, whilea temperature responsive devicep32 is mounted at a suitable point in theV combustion chamber 12 for sensing the temperature of the combustion gases. The device 32 is operablyconnected through a conduit 33 to the fuel regulator and'starter control.28. A suitable igniter 35 is provided forI initially igniting the combustion gases in the chamber'12. The igniter 35 may beA of conventional type and is operably connected through a suitableelectrical conduit to the starter control28.

Also ar'rangedfor driving the turbine shaft.22in starting is a suitable starting mechanism indicated herein generally by the numeral 36 and operably connected through electrical conduit 37 to the starter control. The starting mechanism 36 may be arranged to engage the shaft V22 in driving relation during starting and disengage the shaft 22 after starting by suitable means, well known in the art.

The fuel input lines 16 may be controlled by a suitable fu'el equalizer valve 38 of *a type disclosedi'and claimed in my copendingV application Serial No. 158,274 filed April 26, 1950"a n`d having maximum'speed limitingk meansfojp eratively connected lto the shaft'22 through a Shaft 38A asl explained in the latter application.

The fuel equalizer valve 38 lmay be controlled A`by the automatic starter control 28 through an' electrical conduit 39 operatively connected to the control 28. The equalizer valve 38 may be supplied with fuely under "pressure of a vFigure 6.

pump 49 through a throttling valve 4l in a supply conduit 42.

The throttling valve 41 may be of conventional type operatively controlled through a shaft Slby a reversible electric motor 82 connected through an electrical conduit 45 with the controll system indicated generally by the numeral 28 and hereinafter explained with reference to Figures l and 3` Instead of a throttling valve, there may be used a variable displacement pump 40A controlled by the motor 82 'to vary the supply of fuel to the combustion chamber 12 in accordance with the demands of the regulator 28, as shown diagramm-atically by Figure ll. A manually operable control indicated in Figurelt generally .by the numeral 46 may be adjusted by the pilot flight to vary the setting of the regulator 28 to select theregulated combustion chamber temperature. The-control 46 may be of a type shown in detail in Figures 5 8 to effect the several control functions as hereinafter explained.

As will appear hereinafter, the control system is dcsigned for live phases of operation as follows: 'y

1. Cut-off-when the engine is at rest and the fuel line has been closed by the equalizer valve 38 and throttling 59 in direct relation to the difference between such tem- Y Pel'atul'es.

valve 41 and the control lever 46 has been adjusted to the cut-oil position as indicated by letter A of Figure 6.

r2. Starting operation-the system of control for which is shown by Figure 1 with the controllever 46 adjusted to start Aground idle position indicated by letter'B of Figure 6. i Y

-3. G round idle operation effective immediatelyrafter the' startingcycle has been completed-fthe system of control for which is shown in Figure 3 with the several switches adjusted as shown in dotted lines by thev designation (3) and with the control lever 46 remaining in the previous position B. l Q

4. Normal ground operation-the systempf' control for which is shown in Figure 3 with the several switches adjusted to the position shown in dotted lines by the designation (4) and with the control lever 46 adjusted` to theground operation position indicated by letter C of Mal-Movement ofthe control lever 46 from position C to position D controls the angle of propeller 21 in r'ev'erse'pitch fortaxiing only. l i 4(6). Movement of the control lever 46 from position C to position4 E controlsithe angle of propeller 21 in forward pitch lfor taxiing only. Y

Y 5. Flight operation-the system of control foi' which is shown in Figure 3 with the several switches adjusted to positionsA shown in solid lines by therdesignation k(5) and with the `control lever 46 adjusted 'fron'rp'osition` E offFigure 6 to F for flight minimum power and toward position G to progressively increase the flight' power to maximum., v A.

p System of control for starting operation- Figure1o:

Referring to the drawing of Figure 1,.V there is' shown diagrammatically as disclosed and claimed in the'coperiding application Serial No. 158,273 a system of control for starting a turbinetype engine in which the temperaturere'sponsive elements 32 and 30 are shown as thermo couples connected in 'a loop circuit including control windings 50 and Sil'of magnetic amplifiers' 52 and 53.V'I `he magneticampliiiers 52 and 53 include serially connected excitation windings 54 and 55 connected across a main source of constant frequency alternating current. The magnetic amplifiers 52 and 53 also include D. C. bias windings 56 and 57 and the controlled windings 58 and 59 inductively coupled to the excitation windings 52 and 53,.-respectively. The thermo couples 3l) and 32 are connected in opposing relation so that the control signal energizing the windings 50 and S1 will represent the difference between the temperatures at the compressor inlet and at the combustion chamber 12 which will in turn vary the induced voltage in the `regulated windings S8 and The windings 58 and 59 are serially connected to one of the inputs of a mixer circuit indicated generally by the numeral 60. The mixer circuit 60 may be of a conventional type or may be of a type such as disclosed in the copending application Serial No. 156,260 filed April 17, 1950, by William E. Brandau, j j

The other input to the mixer circuit 60 is grounded during starting operation by a switch 61 closing grounded contact 62. The opposite end of the serially connected control windings 58 and 59 is connected through a switch 63 which during the starting operation closes a contact y64 and through a second switch 65 which during the starting operation closes a contact 66 so as to connect in series with the control windings 58 and 59 an output winding 67 of a rate generator, the purpose of which will be explained hereinafter.

. The opposite end of the generator winding 67 is'fconnected through a conductor 63 to a point on al potenti:- ometer 69 which potentiometer is connected across a'secondary winding 70 of the transformer 71. The transformer 71 has a primary winding 72 connected Hacross the main source of constant frequencyalternating rcurrent so as to induce in the secondary winding 70 a voltlt will be seen then that upon the voltages induced in the winding 70 and control windings 58 and S9 being unbalanced asignal voltage will be applied through the mixer system 60 to output lines 83of the mixer system to the input of a suitable ampliiier 84. The amplifier 84 'may be of a conventional type or may be of a typcsuych as disclosed'in Ui S. Patent No. 2,493,605 granted January 3, ,1950, to Adolph Warsher and assigned to Bendix Aviation Corporation.

The outputV of the amplifiery 84 leads throll'gh".output lines 8S to a limiter potentiometer vandthence to`an input of an amplifier 87, likewise of conventional type. Output'88 from the amplier 87 leads to the control winding 89 of a two phase actuator' motor 82 having vits fixed phase winding 9u connected across Vthefmain'"source of alternatingcurrent. j v f f 4The-actuator motor 82 is arranged to drive 'through'.the shaft 81 the throttling valve 41 so as to increase' ordecrease the `dow of fuel to the enginedependingupon Vthe direction of unbalance of the main control system vinc'zllidingV contfrolewindingstl, 59 and70.V In actuating theI shaft 81 in an opening directiom for example, toincrease thenfuel` supply to the engine in response to a call `for increase in temperature, the shaft 81 will also adjustably position the follow-up rotor winding 79 so astoincluceY in the winding77 of voltage tending to counteractthefsilg'nal voltage callingV for increase in fuel'or temperature fand therebyl in effect decreasing thetemperature setting 'with movement of the valve in an'opening direction by the motor^82. Similarly, upon the temperature tendingfto ,exceed the selected 'ceiling temperature,l lthe motor SZ'jwill position Vthefvalve in a'closin'g directionnd ythel followup'winding '79 in a direction tendingto inducelavoltage in the winding 77 counteracting the signal voltage calling for a closing movement of the throttling valvev andtendto'increase the temperature setting. y 'Y fuel Aandtendiperattue, the controlledyariable temperaof the winding 70 to a lower value.

ture will decrease with increase in speed during' this transient causing adjustment of the actuator"'motor"82 in a direction calling formore fuel while positioning the follow-up winding 79 so as to reset the selected temperature This is desirable to prevent stall during tire-up.

Referring now to the drawing of Figure 1, the yball governor 27 driven by the shaft 26 senses the speed of the turbine and is arranged toadjustably'position a rotor winding connected across a main source' of constant frequency alternating current. The winding 100 forms a rotor portion of a variable coupling transformer 102 having a stator winding 104 inductively coupled thereto. The stator winding 104 is operatively connected through suitable electrical conductors to a stator winding 105 of a second variable coupling transformer 107 having a rotor winding 109. Rotor winding 109 is connected through suitable conductors to the input of an amplifier 111 which may be a conventional type or of a type'such as shown in the said U. S. Patent No; 2,493,605. The output of the amplifier 111 is connected through conductors 113 to a control winding 115 of a two'phase relversible servo motor 117 having another winding 119 connected across the main source of alternating current.` As indicated diagrammatically in Figure l, the servo motor 117 drives through a shaft 121 suitable rotary switch elements 123, 125, 127, 129, 131 and 133 and also the rotary winding 109 so as to follow the position of the first winding .100. Thus adjustment of the rotor winding 100 in response to a change in speed as sensed by the governor 27 will cause through the servomotor 117 a like adjustment of the rotor winding 109 to a null position together with adjustment of the rotary switch elements 123-133. Cooperating with the rotary switch elements 123-133 are respective brush elements 135, 137, 139, 14.1, 143 and 145 which cooperate with the relay switch system shown diagrammatically in Figure 2 as hereinafter explained.

Switching system Referring now to Figure 2, in order to effect the automatic starting operation, a cut-off switch indicated by the numeral must be first closed so as to effect energization of a relay winding 151 of the relay mechanism 153 having movable contacts 155, 157 and 158. Such energization of the winding 151 will then cause contact 155 to close contact A while contact 157 closes contact 157A and contact 15S engages an open contact 158A.' The closing of contact 155A by the movable contact 155 will then effect energization of a relay winding 160 through line 162. The closing of contact 157A by movable contact' 157 will similarly cause energization of a relay winding through a conductor 167.

The relay-winding 160 controls movable contacts 170, 171 and 173 and upon energization of the relay 160 the movable contact closes contact 170A, the movable contact 171 closes contact 171A and movable contact 173 engages open contact 173A.

' The energization ofthe relay winding 165 similarly causes movable contacts 180, 181, 182, 183, 184, 185, 186, IS7 and 188 to close cooperating contacts 180A, 181A, 182A, 183A, 184A, 185A, 136A, 187A and 188A. The closing of contact A by the movable contact 180 effects through the conductor and 191 a holding circuit for the relay windings 160 and 165 through the rotary switches 125 and 129 heretofore explained.

Now, when it is desired to start the engine, the cut-off switch 150 is opened causing deenergization of the relay winding 151 whereupon the movable contacts 155, 157 and 15S are biased under suitable spring means not shown, so as to open the contacts 155A, 157A and 158A and close contacts 155B, 157B and 155B. The closing of contact 158B by the movable contact 158 then effects through a conductor and rotary switch 131 and 133 energization of electromagnetic winding 197. The relay winding 197 controls a movable contact 198 which upon energization of the winding 197 Aclosescontact 199 so as to complete "a circit for effecting energization of'a suitabley'star'ting mechanism 36 to drive the Vturbine engine. 'A Qeenergiz'ation of the winding 151 also causes the movablecontact 157 to open the contact 157A and thus break'the circuit through'the conductor 167 to the relay'winding 1,65, which, however, continues to be energized through the rotary switch 129 and the holding contact `180A and 180. Likewise, deenergization of relay winding 151 causes the movable contact 155 to open the contact 155A so as to open the conductor 162 to relay winding 160. Therelay winding 160, however, continues to be energized through the rotary switch 125 and the holding contacts 130 and 180A At a predetermined driven speed of the turbineas sensed by the flyball governor 27 of, say for example, 2000 R. P. M., the flyball governor 27 causes adjustment of the rotor winding 100 ofthe variable coupling transformer 102 and-thereby rotation of the servo motor 117 in a direction such that the rotary switch 125 opens vthe energizing'circuit for the winding 160 whereupon mov able contact 170 opens contact 170A controlling the' circuit for. holding the flow equalizer valve heretofore `de scribed in a shut-off position so that fuel may now flow tothe combustion chamber of the enginev through the 'equalizer valve. Similarly the movable contact 171`opens connected to a conductor 200 which, as indicatedin Fig-A ure 3, leads'to a point 201 on a potentiometerY 202 connectedacross a secondary winding 203 of a transformer having a primary winding 204. The primary winding 204 connected across the main source of alternating current is arranged to induce into the winding 203 an alternating current of such a phase as to cause rotation ofthe actuator motor 82 in a direction to close the throttling valve 41 to passage of fuel. The output of the secondary/"winding 2 03 is connected to input conductor 205 of'an amplier 206 while'the other input line 205A of the amplifier 206 is grounded. VThe opposite output conductor 200 from the secondary winding 203 leads through contact 171A, movable contact switch 171 and conductor v207 to al switch 181 closing a grounded contact 181A'. Corresponding switches are indicated in Figure.3 by dotted lines as connecting line 200 to line 207 and line 207 "to ground. The latter ground ,connection is effected in Figure 2 by the movableswitch contact 181 which closes contact 181A upon energization of the electromagnetic winding 165.

It will be seen then that the output of the secondary winding 203 of the transformer having primay winding 204- is then connected tothe input of the 4amplifier-'206 through conductor 205 and groundedconductori205A. The amplifier 206 may be of a conventional type or may be of a type such asl disclosed in` the U. S. Patent No. 2,493,605 granted January 3, 1950 to Adolph Warsher and assigned to Bendix Aviation Corporation. The output 207 of the amplifier 206 is connected through a phase selector 208 having an outputl 208A leading to the input of the amplifier 87. The phase selector may be of a conventional type or a type such as disclosed in the' copending application Serial No.` 41,329 filed'July 29,- 1948, 'by William E. Brandau and is arranged to permita signal voltage of a phase corresponding to that induced through the secondary winding 203 to the phase selector' 208 to pass, while not permitting the passage, of a signal voltage of an opposite phase. The signal voltage which phase selector 208 permits to pass is of such a phase as to cause the motor 82 to drive the throttling valve 41 in a direction for closing the valve 41 to cut off the passage of fuel to the combustion chamber 12'.

arcanes Now, upon the cut-olf switch 150 being opened and -the'electromagnetic winding 160 being deenergized, as

Va secondary winding 213 inductively coupled to the primary winding 204 and so arranged that there is induced into the secondary winding 213 a voltage having an opposite phase relation to that induced in the secondary winding 203. The output of the secondary winding 213 is connected to the input conductor 205 of theamplifier 206 while the other input line 205A of the amplifier 206 is connected to a common ground connection to which the opposite output conductor 209 is connected through contact 171B, movable contact switch171,l conductor 207 and switch 181 closing ground contact 181A. Corresponding switches are indicated in Figure 3 by dotted lines as connecting `line 209 to line 207 and line 207 to the common ground. "thus, the output of the secondary winding 213 is connected to the input of the amplifier 206. However, the phase selector 208 is so arranged that signal voltages of a phase opposite to that induced ,in the winding 203 are not permitted to pass through the phase selector 208. Therefore, the signal voltages from the winding 213 do not pass to the amplifier 87 from the phase selector 203 and the servomotor 32 may adjust the rotary switch 131 energization of a relay winding 215.

The energization of relay winding 215 causes a movable contact 216 to close a contact 217 for effecting operation of the igniter 35 for igniting gases in the combustion chamber 12 for starting the engine.

A fuel owing to the combustion chamber 12 through the throttling valve 41 and the equalizer valve 38 now starts to burn and the temperature in the combustion chamber rises until the ceiling temperature set by the connection of the conductor 68 'to the potentiometer 69 of Figure 1 is achieved.

It will be noted that, as shown in Figures 1 3, the movable contact 186 closes contact 186A upon energization of the winding 165, causing in turn the energization of the relay winding 220; energization of relay Winding 220 in turn causes a movable contact 65 to close a movable `contact rcounecting into the temperature loop the output winding 67 of a rate generator 226. The rate generator 226 has a winding 227 connected across a main source o f..alternating current and has a rotor driven through shaft 228 by the servomotor 117 at a speed proportional to the acceleration of the turbine 20.

Y The output of the rate generator 226 has a frequency determined by the main source connected across winding 227 and the output voltage is proportional to engine acceleration and is connected in the temperature sensitive circuit by the contacts 65-66. The rate generator ,226 is arranged to introduce a feed back voltage having a pbase relation such as to reduce the selected temperature level with increase in engine acceleration. Since the characteristic of turbine engines is relatively poor efiiciency at low speeds, a fixed operating temperature -st iliciently high to guarantee acceleration of the engine at starting speed results in a runaway acceleration as the rgted speed is approached. The acceleration feed back introduced by the rate generator 226 acts to moderate this tendency. Y

Speed continues to increase, however, at ceiling temperatur'e and itwill be noted that theV control temperature setting decreases with increaser'in" speed :during "this transient since the position follow-'up tends to reset the selected temperature to a lower valuei*y This is desirable to prevent stall during tire-up.

When the turbine reaches a predetermined self sustained speed of, for example, 4000 R. P. M.'the rotary switch 133 opens to deenergize electromagnet 197 whereupon the movable 'contact 19S opens the contact 199 and deenergizes the starter mechanism while the rotary switch 131 opens to deenergize the relay winding 215 whereupon the movable contact 216 opens the contact 217 to deenergize and extinguish the ignitor mechanism 35.

Further, when the speed of the turbine reaches an additional self-sustained speed of, for example, 5500 R. P. iM., the rotary switch 129 opens the energizing circuit for the relay winding 165 whereupon the several 184B and 187B so as to transfer the circuit shown in Figure l to the circuit shown in Figure 3 formormal ground operation.

More precisely, a holding circuit for the relay windings 160, 165, 197 and 215 controlled by the speed sensitive switches 125, 129, 131 and 133 is broken by the opening of contacts 180 and 180A upon deenergization of winding 165 and the` starting cycle cannot be re-initiated without lirst closing the cut-olf switch 150. This arrangement thus prevents accidental re-energization of the starter and ignitor equipment in the event the engine should stall.

Furthermore, the deenergization of the electromagnetic winding 165 permits the movable contacts 181, 182, 183, 184, 185, 186, 187 and 18S under suitable spring means to open contacts .181A-158A, respectively, and close associated contacts. 1S2B-187B, respectively, so as to transfer the connection of the speed transformer 102 and speed follower transformer 107 of Figure 1 from the system shownin Figure l to that shown in Figure 3 for normal operation.

Thus, deenergization of the electromagnetic winding 16S causes the movable contact 181 to open the contact and the movable contact 187 to open contact 187A and close contactv 187B to connect line 200 to line 207 as indicated `schematically by dotted lines in Figure 3.

Further, upon such deenergization of the winding` 165-, the movable contact 182 opens contact 182A and connects the line 76 from the follow-up winding 77 to the stator winding of the transformer 107, as indicated schematically in Figure 3, while movable switch contact 183 opens contact 183A to disconnect the rotor winding 109 of the transformer 107 from the input of the amplifier 111 and close' contact 183B to connect the rotor winding 109 across the main source of alternating current. Thus, upon deenergization of the winding 65, the connection of rotor winding 109 is transferred from that shown in Figure l to that shown in Figure 3. .A

Moreover, movable contact184 upon deenergization of the relay winding closes contact 134B to connect connections of the transformers 102 and 107 from that shown in Figure l to that shown schematically in Figure 3 upon deenergization of the winding 16S. i l

Furthermore, the movable contact 186 opens the con tact 136A so as to potentially deenergize the electromagnet 220 in the event the pilot should transfer control from ground idle operation to vnormal ground operation by opening the switch 225. In the closed position of the switch 22S, the system remains in ground idle operation and the electromagnetic winding 220 continues energized.

The movable contact 187 upon deenergization of the relay winding '165 further opens contact 187A and closes `the contact 187B so as to in effect cause thelswitchof Figure 3 indicated in dotted lines to close the contact for Normal ground operation To effect normal ground operation, pilot mayvn'ow move a selector switch 225 to an open position deenergizing electromagnetic winding 220 causing a movable contact 230 to open associated contact 230A and close line position indicated by the numerals 171 and 230 of Figure 3` so as` to close a circuit through the contact indicated by numerals 171B and 230B which raises the speed ceiling to a higher value of, for example, 7088 R. P. M.

Furthermore, the de-energization of electromagnet 220 causes a movable contact 232 to open associated contact v232A and close associated contact 232B which effects a 'circuit for controlling the propeller pitch by a suitable mechanism indicated diagrammaticallyin Figure 9 and explained hereinafter. The de-energization of the electromagnet 220 causes movable contact 65 to open a contact 66, shown in Figure l and heretofore described, and close a' second contact 66A, as shown in Figure 3, which increases the temperature ceiling of the regulating system from that of the setting of Figure 1 to that of setting of Figure 3 with switch 63 closing contact 64 as indicated by dotted lines.

The de-energization of the electromagnet 220 also causes movable contact 235 to open an associated contact 235A which potentially de-energizes a second electromagnet 240 in the event the pilot should open a switch 242 to transfer from normal ground operation to flight operation.

VDuring ground operation with the switch 242 closed, it is expected to maneuver the airplane by maintaining the preset speed of, for example, 7088 R. P. M. of the over-speed governor and varying power by adjusting the blade angle ofthe propeller to give forward and reverse thrust at the same time. The speed is isochronous (dead beat, no droop) as the follower 77 is wiped out by the speed control circuit.

F light operation For ight operation the pilot may open switch 242 to de-energize the relay 240 whereupon movable contacts 245, 247, 63, 251 and 61 are biased by suitable spring means to open associated contacts 245A, 247A, 64, 2151A 7200 R. P. M.

Moreover, the opening of contact 247A and the closing of the contact 247B puts the propeller pitch g'overnor in normal speed control as hereinafter explained.

Further, the opening of contact 64 and the closing of contact 64A in effect causes a like designated switch 63 in Figure 3 to close a contact 64A to change the temperature of a control system from a fixed ceiling to one which is variable by movement of the pilots power control lever 46 as indicated in Figures 3 and 7.

The de-energization of the electromagnet 240 causes a movable contact 251 to open contact 251A and close contact 251B to cause a like indicated switch 251 in the system of Figure 3 to close a contact 'for transferring the reset transformer from the arrangement` of ground operation to that of ight operation indicated' in Figure 3.

Furthermore,rthe de-energization of electromagnet 240 `ates at a` steady -10 closes a movable contactV 61 to open contact A 62 ,and closes contact '62B to in effect cause alike indicated switch 61 in the system of vFigure 3 to connect i'ritothe mixer system 60 signals for operation vof the regulator system during normal flight operation;

Operation of overspeed control During ground idle operation the secondary winding 203 providesV a signal voltage of aphase which is'opposed by the signal voltage of the transformer `102'whicliis of oppositephase'and, therefore, so long as the signal voltage across the output lines' 200-'205 of the primary winding 203 does `not exceedfthe' signal voltage of' the transformer 102 no signalA passes throughthe phase selector 208. However, as the speed ofthe turbine :20' :increases the rotor winding y'is adjusted` ys.'o""`as"to decrease the voltage induced'in the' stator'winding 104 until at the predetermined maximum speed of, forexample, 6000 R.' P. M. the signalvoltage at: the'outpilt lines 200-205 exceeds that of the'signal vo1tage"from the transformer 102 so thatvthereupon a signal voltage passes through the phase s electo'r'208. Such l signal voltage passed'by the pliase selector 208 efectsthe amplier 87 and actuator motor 82 so as to 'adjust theA throttling valve 41 to decrease'the fuel supply to decrease the engine' temperature and speed lso lthat' duringwnormal ground idle operation the engine'operates at asteady predetermined speed of, forexample, 6,000 R. P. M'.'

Now upon the' switch 230ffbeing" adjusted to' close contact 230B for connecting'line 207 to line 209 asdring normal ground operation a signal Vvoltages fsupplied by output lines 2054-209 of the 'secondary winding 213 instead o-f the`seco'ndary winding 2303f 4The signal voltage supplied by the secondary winding 213 will bein phasewith that supplied by transformen 4102 at the rst predetermined speed'of, for'example, A6000 R. P. M., but as the speed of the turbine`p'2`0finc'reases adjustment of the rotorwinding 100 bythe yball governo'r 27 causes an inversion in the signal voltage induced in the stator winding 104 of the transformer 102 until asa` predetermined speed of, for example, 7088 RIP. M. is approached,vthe signal voltage induced'in the stator winding 104 of opposite phase tends to balance that induced in the secondary winding 213 and upon vondai'y winding 213 and passes the phase selector 208 so as to cause actuator motor 82 to move in a direction to-decrease the fuel supply to the combustion chamber `12 to'decrease the engine temperature and speedso that during normal ground operation the engine operpredetermined speed of, for example, 7088 R. P. M.

` Now` upon the switch 245 being adjusted so as to open contact 245A and close contact`245B so`as toy transfer from output line 209 to output line 209A a higher'predetermined speed is selected of, for example, 7200 R. P. M. and upon the rotor winding 100 being further adjusted by the ily-'ballgovernor in aspeed' increasing direction'the` voltage induced in stator winding 104 exceeds that across the output lines 205 and 209A to limit the speed of the turbine at the predetermined speed of 7200 R. P. M.

' It will beseen from the foregoing that the speed sensing unit of` Figure 1 is the same ily-ball governor 27 and transformer 102 which is used during normal operation to supply vspeed sense to the electronic control system in terms of a voltage signal. For the start cycle, how-- ever, this speed transformer 102 is coupled to the reset transformer 107 which acts as servo operated follower of speed as shown in Figure l. The reset transformer 107 during normal ground idle and ground operation is coupled in series with the follow-up transformer 77 to affect the reset amplifier and thereby the reset actuator motor so as to cause adjustment of the rotor 'winding 109`in a 'direction to cancelout the follow-up voltage induced in winding 77 by adjustment of the rotor winding 79 by the valve actuaton` motor S82* 'and thereby remove the follow-up temperature drooping effect. In the starting operation such follow-'up temperature drooping effect is not removed and` as heretofore explained it is a desirable characteristicV in" the starting operation to have such temperature droop with increasing speed.

In the start cycle a position follower isgrequiredj and not a voltage followerand to achieve this fthe stator windings 104 and 105 (speed and reset) are interconnected as shown in Figure 1. The rotor 10,0 of the speed transformer has an excitation voltage applied, whilethe rotor of the reset transformer 105 .is connected "during the starting operation to the input of the Areset ampliiier 111 as shown in Figure l. In this way the reset actuator motor 117 acts to cranl; the reset rotor 109 through shaft 121 to a null position which corresponds to the transformer 100 rotor position and the result is a servo operated speed follower to open and close suitable switches for effecting the several functions in the starting operation heretofore described.

The selected temperature for the start cycle (the controlling factor) is low` enough to prevent compressor stall, and at the same time high enough to provide an accelerating torque in the engine throughout the start cycle. The actual control circuit itself is a modified version of that used in normal'operatipn. The effective follow-up signal used in the ground` idle and ground operation circuit, is not available duringa start, since the reset transformer 105 has been taken out of thejcircuit. A direct follow-up signal is supplied to thecir cuit in its stead by the adjustment of the rotor Winding 79 relative to the winding 77 by the actuator motor 32, as shown in Figure l. manner introduces temperature droop. The maximum variation in temperature directly due to` this droop does not exceed degrees Fahrenheit.

The engine after starting will continue to accelerate up to the ground idle R. P. M. At approximately 500 R. P. M. below groun-d idle the transfer relay controlled by rotary switch 129 swiches over to normal operation, ground idle. The starter 36 and ignitor 35 are both arranged to be cut out by suitable rotary switch relay operated means at some point below the transfer R. P. M. The key to a smooth transfer of control functions at this point is the relative position of the reset transformer 107. The position of the reset transformerk 107 as a speed follower should closely proximate the position of the reset in the follow-up loop for average ground idle operation.

Having completed the start, all relaysused in the start cycle are de-energized and in addition the voltage supply tothe start rotary switch is cut off. Repetition of-the start cycle, or any portion of it may only be initiated by going through the cuto1 position.

Fiz'ght Voperation When the switching mechanism has been adjusted to the position for effecting normal iiight operation, as indicated in Figure 3, it will be seen that the ceiling temperature selector 68 for ground operation is cut out of the temperature circuit by the switch 63 and in 'its stead there is operahly connected a transformer V300 having stator windings 392 and rotor winding 303 connected across the main source of alternating current. The rotor winding 303 may be variably positioned through operation of the lever 46 to select the desired-temperature.

Further connected in series with the stator windings 302 of the transformer 306 is an output winding 305 of a rate generator 307' having a winding 309 energized from the main source of alternating'current and a rotor 310 driven by the actuator motor $2 so as" to apply to the temperature responsive loop a follow-up signal voltage proportional to speedof change in position of the Using a direct follow-up in this throttling valve 41 and tending to retard rapid changeof position of the throttling valve 41 so as to maintain Vstability of control. p

The output voltage of the rate generator 307- is also applied across the cathode and grid of an electronic valve 3i@ so as to cause a cathode plate voltage in the primary winding 312 to produce in the secondary winding 4314 of the'transformer 316 a follow-up signal voltage. Such follow-up is in turn applied in the overspeed loop rso as to tend to retard rapid change in the position of the throttiing valve 4i under overspeed conditions an-d thereby provide stability of control in the overspeed governor.

Furthermore, the adjustment of the switch 6,1 toopen `grounded contact 62 and close contact 62B tothemixer system 60 permits the follow-up transformer 77f79, to appiy a follow-up signal to the temperature loop .which is in turn wiped. out by the action of reset transformer 107 having the rotor winding driven by the reset motor 117. lt will be also noted that the rate generator 226 applies through the output winding 67 a rate signalto the input of the reset amplifier 111 proportional to the driven speed of the rotor 109 so as toV retard rapid change of position of the reset winding 109 and thereby provide stability of control.

The structure hereinbefore described with reference to Figures 1 to 4 is disclosed wd claimed lin the said copending application Serial No. 158,273 assigned to Bendix Aviation Corporation.

Improved features There are described and claimed Aingthe aforesaid divisional application Serial No. 268,303 features of a single lever controlled starting and power control device foran aircraft engine hereinafter described with reference to Figures 5 to i0 for use with the control system hereinbefore described and shown with reference to Figures 1 4.

The improvcdunit is used to convey intelligence tothe control system through a system of switches 150, 225 and 242 which are actuated by the manual positioning of control lever 46 and also by positioning the rotor element 303 of the temperature selector transformer 300 which is geared to the manually operable control lever 46 as is also rotor arm 402 of a potentiometer 400, shown in Figures 7 and 9, for scheduling the adjustment of the pitch of the propeller 21 during ground operation and features of which are described and claimed in the said other divisional application Serial No. 268,304.

The present application is directed to novel means by which the limiting of power and temperature in the` engin'e is achieved. In order to avoid superimposing one control on another, the value of selected temperature which would produce both a safe limit of combustion temperature and safe limit of power output is separately computed by a novel stop computer shown diagrammatically in Figure 10, as a function of several variables affecting these two limiting conditions. A servo operated stop in the control unit is then positioned by the computer so that the control lever 46 cannot be advanced beyond the limited point and so that the control lever 46 remains within a safe operating region. The action of the computer and-stop mechanism is such as not to introduce any problems of stability or interference which might otherwise result through the mixing of the electronic circuits involved.

Single lever control zmz't for conditioning automatic control system As shown in Figure 7, the control unit includes a quadrant shaped casing 357 having formed therein a-slot 359 13 l a pin 370 Vat a point intermediate the opposite endsnof the lever 46. One end of the lever 46 has a ball 372 affixed thereto for convenient nzanual operation of the lever 46, while the opposite end of the lever 46 projects from the casing 357 through a slot 373 and is connected through a mechanical linkage 375 to'an emergency control not vshown herein, but which may be of a type arranged to take over control of the engine upon malfunction of the electronic or primary control with no initiating action required ofthe pilot. This means that the emergency system controls the engine over the same parameter and to the identical state condition that the control lever 46 vdesignates for the main control system. Thus, malfunction ofthe electronic or main control system, as indicated Y by failure to maintain the selected 'state condition will Y automatically cut in the emergency control which may be of a type disclosed and claimed in U. S. patent application Serial No. 192,508, filed October 27, 1950.

The lever 46 may be pivoted on the pin` 370 as the lever 46 is adjusted laterally in the slot 359 from position B to position C and from position E to position F, as indicated in Figure 6. Such lateral pivotal adjustment of the lever 46 will cause the plate 361 to move laterally with the lever 46 with a snap action, as indicated in Figures 7 and 8.

f The latter snap action is effected through operation of a U-shaped toggle bar 377 pivotally mounted in a bearing member 379 carried by the casing 357. .The toggle bar 377 has arms 381 and 382 projecting from the opposite ends thereof. Projecting from the free ends of` arms 381 and 382 are pins 384 and 386 positioned in suitable slots 388 and 389, respectively, provided in the plate 361 and cooperating with the plate 361.

Spring elements 391 and 393 are connected to the respective arms 381 and 382 by pins 394 and 395, respec- Vtively, and to the casing 357 by pins 397 and 398, respectively.

As shown by Figure 8, lateral movement of the shift plate 361 slidably mounted on the pins 363 and 365may be effected through operation of the lever 46 as upon adjustment thereof from position B to' position C or from position E to position F of Figure 6. Such lateral movement will causethe spring elements 391 and'393 to bias the shift plate 361 and thereby the lever 46 to the latter position C or F with a snap action as the arms 381 and 383 pass through the center point of the bearing member 379.

Three switch mechanims 150, 225, and 242 are mounted within the quadrant shaped casing 357 and are arranged for operation by the positioning of the control lever 46.

The switch mechanisms 150, 225 and 242 serve to determine the operating conditions of the control system p as heretofore explained with reference to Figure 2.

The switch mechanisms 150, 225 and 242 may be of a conventional snap action type, well known in the art in which the switch mechanisms 150 and 225 are nor' mally biased by suitable spring means to a circuit open position while the switch mechanism 242 is normally biased by suitable spring means to a circuit closed position.

The switch mechanism 150 has a switch actuating member 150A which is engaged by the lever arm 46 when in` .the cut-off position A of Figure 6 so as to cause the switch mechanism 150 to be actuated to a circuit closing position.

Upon arcuate movement of the lever arm 46 from the cut-off position A to the start position B, the lever arm 46 disengages the switch actuating member 150A, whereupon the switch mechanism 150 is released to a circuit open position for initiating operation of the automatic starting control as heretofore described with reference to Figures l-4. The switch mechanism 225 has a switch actuating member 225A which is engaged by the lever 46 when in the start-ground idle position B so as to cause the switch mechanism 225 to be actuated to a circuit closing posi-V .tion forr effecting; fground idle operation of Ythe control Y anism, 225 lis released to a*:ciruitYoperrpositionl for lcronditioning they control systemfor ground operation upon the starting operation being-.effected through the Vautomatic starting control, asdescribed with reference to Figures 1-4.

. The switch mechaninsm 242 has 4a, switch actuating member 242A operated by a resilient j arm 242B` which is` actuated by the arm 382 of the toggle bar 379 so as to cause the switch mechanism 242 to be actuated to'a circuit open position, upon lateral movement ofthe lever arm 46 from the taxi forward p osition E .toV the fiight operation position F causing in turn the shift plate 3,61V andthe toggle arrn 382 to move laterally to effect actuation offl the resilient arm 242B to open switchj 242.

During arcuate movementfofthe lever arm 46 in the ground operation, range of positions C, 1D and E, the resilient arm 242B releases the switch actuating member 242A so as to permitthe switch mechanism 242 to as sume its normal closed circuitk position for effecting ground operation, as heretoforedescribed with reference to Figures 144.

Propeller pitch `control llever 46 in ground"operationv'efectsthrough shaft 369 and gearing'3'99 theposi'tion Tofan adjustable contact arm on a potentiometer 400 controlliri'g'the' pitchl of thepropeller blade 21. yThe adjustable contact arm is yindicated diagrammatically in Figure 9fby' th'e numeral 4'0'2 and'is electrically connected-"through a conductor V403 "to the relay contact 232Bf The potentiometer 400,* asshwn in Figure 9, provides opp'ositearmsof 'normally balanced'bridge circuit 404'which'rnay be' of conventional type. The bridge'circuit 404; includes av second potentiometer`405'having'an adjustable'arm 407"`anda source of alternating current connected byconductors 409 and 410 across the bridge circuitj404.

YUpon the'control system of Figure 2 being in ground operation with"switchf232 closing contact 232B' and switch 247 closing contact 247B,"a`s indicated in Figure 9, the arm 402 and arm 407 are `connected by conductors 412 and 413 to the input df a suitable' amplifier l415 of conventional type having youtput conductors 417 and 419 connected to a'control winding 421 of a Atwo phase motor 425 of conventionaltype. Themotor425 has a fixed phase winding` 427 connected across the source of alternating current;

The motor'425 is arranged to adjusththrough a shaft 429 and linkage 430 the setting of the propeller pitch control me`chanism'f29 upon an adjustment of the lever 46 and contact armf402 un balancin'g,the bridge circuit 404. The arm 407 is likewise 'adjusted' by thel motor 425 through a" shaft,433,"irfdicated by dotted lines in Figure 9 in a directiontov rebalance the bridge cir'cuitl`404.y

A positioning ofthe'cc'introl` lever 46m thefground operation range C-E effects through the mechanism29 the angle of the propeller blades "21'in a vpositive pitch range for the taxiing of the aircraft von the ground in a forward direction, while adjustment of the control lever 46 in the ground operation range C-D effects through the mechanism 29 the angle of the propeller blades 21 in a negative pitch range for the ltaxiing of the aircraft on the ground in a reverse direction. The adjustment of the control lever 46 to the position C effects adjustment of the propeller blades 21 to a neutral position.

However, during ground idle operation with the control lever 46 at the position B the switchv225 is closed causing the relay switch232 togclose contact 232A and tip'enV co'ntct`232B`." The Contact 232A is connected through a conductor 435 to a fixed point on the 'potentiometer 400 for the selection of minimum torque or a minimum angle of pitch for the propeller blades 21 effective during start and ground idle operation.

Adjustment of the control lever 46 from the ground operation position E to the flight cruise minimum power position F opensl the iiight operation switch v2,42 thus de-energizing the relay winding 240 of Figure 2 and causing relay switch 247 to open contact'247A and close contact 247B. The contact 247B is connected through a Vconductor l437 to a lixed point on the potentiometer 409 for effecting through bridge circuit 4&4 and motor 425 a speed setting adjustment of the control mechanism 29 for flight operation'.

The point at which conductor 437 is connected to the potentiometer 400 is such as to cause through motor 425 an adjustment of the mechanism 29 in excess of that elected in either start-ground idle or ground operation. Upon such adjustment of the mechanism 29 for flight operation, the mechanism 29 serves to maintain the speed of the engine at a predetermined value'by varying the pitch of the propeller 2l through the operation of suitable speed responsive means well known in the art. The mechanism 29 is not shown in detail,

but may be of a suitable type well known in the art.`

During ground idle and groundoperation, the pitch of the propeller 21 is adjusted through operation of theV mechanism 29 to predetermined angular positions, for example, during start 'groundidle operation to 5 blade angle, while during ground operation blade angles from 25 to +9, respectively depending on, the position-ofthe control lever 46 within the range D-C-E. During such start-ground idle vand ground operation the speed of the engine is controlled by a rspeed governor in the control system of Figures 1 and 3 which variesthe fuel to maintain preselected speed settings and also controls the fuel on accelerations to maintain selected maximum temperatures. In flight operation, the speed of the engine is maintained at a predetermined value by varying the load of the variable pitch propeller 21 controlled by the propeller control mechanism 29 in response to the speed of the engine. The control system of Figure 3 during such flight operation varies the fuel llow so as to maintain a selected turbine temperature corresponding to the position of the power control lever 46.

Engine temperature control and safety stop means Motion of the control lever46 in the ight cruise range affects the temperature setting of the control circuit by adjustment of the temperature selector transformer 300 which has the rotor winding 363 mechanically coupled to the control lever 46 through the gearing 399 and shaft 369. The transformer 30G produces a signal input to the temperature control circuit, as heretofore described with reference to Figure 3.

In operation, however, the maximum position of the control .lever 46 is limited, as shown in Figure 7, by a servo operated stop pin 440 carried by an idler gear 442 ,rotatably mounted onpthe shaft 369 and adjustably positioned through gearing 445 by a motor446 under control of a maximum engine power and combustion 4.temperature computer mechanism, shown schematically in Figuredt). A' dog 447 'clamped to the shaft -369 :is arranged to come intocontact with the stop pin 44o in the limiting position. The motor 446 is further arranged so as to adjust through gearing 449 the rotor element of a follow-up transformer 450 as shown schematically in Figure 10.

The temperature selector transformer 360, propeller pitch control potentiometer 400, servo motor 446 and follow-up transformer 450, together with the gearing .399, 445, 449 and idler gear442 and dog 447 are mounted l within a control boxv455 aixed to the casing 357, r'as shown in Figure 5.

. Computer mechanism The prime function of the control system, as previously stated, is to regulate thefuel ow to the engine in such quantity as to achieve-a selected power setting within safe limitations of the engine. speed are limited by actually measuring these quantities and restricting fuel owwhen the selected limitshave been reached. However, under certain conditions, it is possible to be within these limits and yet exceed the maximum allowable shaft torque that may safely be applied to the engine output shaft or exceed safe op- It is the purpose ofthe erating engine temperatures. stop computer, shown schematically in Figure l0," to compute and impose these limiting factors into the primary system. The stop computer senses ram inlet pressure, compressor inlet temperature and' tail`pipe tem-v perature and converts these into proper positioning of the mechanical stop 440, which acts to limit fuel flow so as not to exceed'the permissible'values vvas calculated by the computer. If flight conditions change to make the pilots selected power unsafe, the stop computertwill automatically reset the effective position of? the control lever 46 to a new maximum safe value by yoverriding -theV previous position of the lever- 46.'

The criteria lfor safe engine operation `are vrnaxiriu'iin safe temperature and maximum safe 1power-jas' -defined by certain constant factors dependent upon thefcharacteristics of theengine' under consideration and certain` variable factors,: asV indicated below wherein: l P1=Ram air inlet duct pressure in pls.4 i. abs. i

T1=Ram air inlet duct temperature in degreesranltine. T3=Turbine inlet temperature in degreesv rankine.

T4=Tailpipe or exhaust gas temperature in degrees rankine. j i

Since the control lever 46 selects (T s-T 1) it-follows that the maximum allowable (Ta-Tr) must be rthe computed quantity which will stop the control lever 46 at positions corresponding to the safe values of (T3-T1 for both maximum power and-temperature.

Such safe values vary with the following factor'szf l. Maximum allowable T3 varies with the factors 2. Maximum allowable power varies with giura-Toti gym-To The measured quantity T1, as shown diagrammatically in Figure 1G, is induced into the computer by an air inlet temperature transmitter which includes a variable coupling transformer 46o having stator windings 461 and 462 inductively coupled to a rotor winding 465 connected across a main .source of alternating current through conductors 468 and 468A. The rotor winding 465 'is'adjustably positioned through shaft 466 by an air inlet temperature sensitive bimetal spiral 467 of conventional type and which may be positioned in the air inlet duct Temperature and with 17 as indicatedin Figure 4. There yis .induced in thestator windings 461 and 462 a voltage which is equivalent of l T1 and respectively.

The reciprocal is derived by curve fitting, a method well known in the art. The sine function developed by the resolveror transformer 460 is displaced and expanded 4in`rectangular `co ordinates so that over the required range of operation la portion of the sine function approximately matches the required rectangular hyperbola.

The output of stator winding 461 is connected to the input of an amplifier 470 of conventional type subject to a biasingvoltage introduced through the transformer 472 and resistor 473 to avoid the zero point of the variable coupiing transformer 460. The output of the stator winding 462 is connected to the input of an amplifier 475 of conventional type and is subject to a biasing voltage applied through resistor 478 and transformer -480 to avoid -the vzero point of the transformer 460.

The measured quantity P1 is inserted into the output of amplyier 47E) of the maximum power loop and the -output of the ampliiier 475 of the maximum ktemperature loop by an inlet air pressure transmitter including two `transformers 432 and 484 having rotor windings 486 and y437, respectively, 'mechanically coupled by a common rotor shaft 439 which is in turn rotated by a pressure sensitive Vbellows 491 subject to inlet air pressure, as indicated in Figure 4, applied through a conduit 493. The rotor Winding 486 is connected to the output of amplifier tf/tl and is inductively coupled to a stator winding l494 while the rotor winding 487 is connected to thevoutput of amplifier 47S and is inductively coupled to the lstator winding 496.

yFor small ratios of 'Pi of the order v2.5 1` the factor may be accomplished with the approximate form I1 (A+B sine Pi) which expanded :is [A Ti-l-BTi sine Pil.

The value BTi sine P1 is derived `by imposing an excitation cn the rotor winding 486 whichis proportional to Ti `and positioning therotor winding 486 by the :pressure transmitter 491 proportional to Pi so that the vinduced voltage in .the stator Winding 494 is equivalent to the factor BTi .sine 1. Now to vthis .signal voltage `there is added through conductor 497 and .resistor 498 a biasing voltage which is proportional to T1 4and :represents ithe factor AT1 so that the resultant signal approximates There is Vimposed `on the rotor winding 487 a'nfex'citation voltage proportional to 18 while there is induced in the stator winding 496 by the rotor winding 487 a voltage 'proportional to There lis further applied tothe stator winding 496 through conductor 497 :andresistor A499 'an lopposing signal voltage proportional to T1 so Athat the output signal voltage of stator winding 496 is proportioned to Pi rr It will be :seen then -that ythe measured quantity of the signal for themaximum temperature -loop of P1 .T1 T1 is effected at the output Yof :the winding i496 to which there fis -applied fa bia-sing voltage through resistor 500 and transformer 501 -to avoid the zero'point-of the variable .coupling ltransformer 1484. A similar rbiasing voltage :is applied through 'resistors '503 `and .transformerl 505 to the output of the stator winding'494 of the maximum power loop.

'In'order to meet the formula -for themeasured quantity of maximum power, there is added to the'output of the stator .winding 494 a :signal voltage equivalent to the .difference between 'air inlet temperature T1 and that Vof .the tailpipe -or .exhaust gas temperature T4. Since .this quantity cannot feasibly be .measured vby variable coupling transformer .angular displacement due 'to the yhigh .temperature valuesof `the tail -pipetemperature a -thermo- .couple 510 mounted inthe air inlet anda thermo-couple Sil mounted in the tailpipe, as shown in .Figure 4, are provided with v.the .desired characteristics. The thermorcouples 510 and 5-11are connected .in Opposing `relation so .that .thexcontrolsignal energizing output -,lines 5172 and 514 .will represent 4T4-.Ti .or -Athe difference vbetween the temperatures at .the compressor .inlet 5 and at .the `tail- .pipe orexhaust 23. The output of the thermocouples '#510 andSll is connected fby conductors .512.and .514 vthrough ra magnetic amplier 516 of conventional type to .the

output'ofthe .winding 494. .The .output of the .magnetic amplier ."5-16 :is .applied .through conductors 518 .and 519. The .resultant signal Moltageat the .outputlines "516 and 519 is `proportional .to .themeasured quantity gym-Ti) for the :maximum power. The L computed voltage -signalv .ground vand :thejunction of fthe two resistance elements `523 and 525 connected iin series across these ipoints. `Because ythe two loop vvoltages are arranged lof yopposite phase'the diiference :is characterized by the :samefphase as the :larger voltage. .The difference voltage :is now appliedfthrough/input:conductors 527 and 5'29ftoamp1iiier 53'1vand through .a phase selector S32/to a control Winding 533 of a relay 534. The phasezselector r532rmaybe of conventional type and -so-designed that-the difference voltage whenof :the samelphase as the output of Athe maximum .temperature loop .such diference voltage will pass through th'e phase .selector so as -to cause Venergize- :tion of .the yrelay `winding 533., while `the difference voltage lwhen ofsanopposite 1phase and similar totthat `of :the l.maximum power loop will .not be permitted 'to pass through the phase selector 532. The control winding 533 when energized will actuate switch 535 so as to close contact 537 and open contact 539. A spring element 546i normally biases the relay switch 535 so as to close contact 539 and open contact 537. Upon energization of the relay winding 533 indicating that the maximum power loop has computed a lower Ts-Ti value than the maximum temperature loop the switch S39 will close Contact 537, The output of the maximum temperature loop is connected by conductor 545 to the contact 539, While the output of the maximum power loop is connected by a conductor 547 and grounded conductor 548 to the input of a phase inverter S49 of conventional type. Grounded conductor 550 and conductor 551 lead from the output of the phase converter 549. Output conductor 551 leadsto contact S37.' The switch arm 535 is connected by aconductor S55 to a resistor 556 connected across a stator winding 557 of the followup transformer 450 and to which there is applied by the stator winding 557 a follow-up voltage. The resultant of the signal and follow-up voltages are applied through the conductor SSS to the input of servo amplifier 559 of conventional type. The opposite input conductor 560 of the amplifier 559 is grounded.

There is applied to the -input conductor 558 a biasing voltage through resistor 561 and transformer 563 for avoiding the zero point of the follow-up transformer 450. The output of the servo amplifier 559 is connected across a control winding 565 of the servomotor 446, shown as of a conventional two phase type. The motor 446 may have a xed phase winding 567 connected across the main source of alternating current. Motor 446 drives a rotor winding 569 of the follow-up transformer 450. The latter rotor winding 559, as shown, is connected across the main source of alternating current and is arranged to induce in the winding 557 a voltage of opposite phase to that of the control voltage applied through switch 535 and normally balancing the control voltage when stop 440, adjusted by motor 446, is at the safe limit position.

When the stop 440 is not at the safe calculated limit position, the position of rotor winding 569 is such as to cause a ditference voltage to be applied to the input of amplifier 559 which in turn affects control winding 56S so as to cause motor 446 to rotate in a direction so as to cause the follow-up rotor winding 5,69 to be adjusted so as to wipe out the difference voltage when the stop 440 has been adjusted by the motor 446 to the calculated position.

The phase selector 532 and relay 534 are so designed that the loop signal voltage calling for equal or lesser computed (T3-T1) passes through the follow-up system. The phase inverter 549 is required to restore the maximum power loop voltage to the same phase as` the maximum temperature loop voltage.

The final action of the vstop computer is effected in the control box 455 where the computed voltage representing the lesser computed T3-Ti positions the stop 440 at an angle equivalent to that which would represent a safe value for both maximum power and maximum temperature. To illustrate the stop action by an example, assume that in flight condition the pilot calls for more thrust from the engine. He will then advance the control lever 46 to some new position thereby selecting a higher value of (Ts-Ti). If, at the moment the throttle is advanced the variables composing the Equations 3 and 4 have values making each function greater than the selected (Ts-T1) then the pilot could advance the control lever 46 to the limit of its movement.

If, on the other hand, the conditions are such that the computed function value of the lesser (Ts-T1) was less than the pilot selected (Ta-Ti), a forward motion of the control lever 46 by the pilots hand would be stopped at the angle computed by the stop means 44d. In the event the pilots selected (Ts-T0 is safe, but over a period of time changes in the altitude and speed have 20 occurredto make the computed (Ts-T1) less than the original control lever setting then the stop means 440 will mechanically reduce the selected setting to the maximum safe value. The stop computer under dynamic conditions can only retard the control lever 46 and any advance ot the control lever 46 must be made by the pilot.

Although only one embodiment of the invention has been illustrated and described, various changes in the form and relative arrangements of the parts may be made to suit requirements.

What is claimed is:

1. For use with an aircraft engine having a combustion chamber, an air intake conduit to said chamber, a fuel intake conduit to said chamber, an exhaust gas conduit from said chamber, means to control the supply of fuel to said combustion chamber, and combustion gas temperature responsive means to regulatethe fuel supply control so as to maintain the combustion gases at a preselected temperature; a control mechanism comprising a manually operable control element, means to select the combustion chamber gas temperature, means operably connecting said last mentioned means to said control element, stop means cooperating with said control element to limit adjustment of said control element in a temperature increasing sense only, and engine operating condition responsive means to adjustably position said stop means so as to limit the maximum adjustment of said control element to a predetermined safe value under the prevailing operating conditions.

2. For use with an aircraft engine having a combustion chamber, an air intake conduit to said chamber, a fuel intake conduit to said chamber, an exhaust gas conduit from said chamber, means to control the supply of fuel to said combustion chamber, and combustion gas temperature responsive means to regulate the fuel supply control so as to maintain the combustion gases at a preselected temperature, a control mechanism comprising a manually operable control element, means to select the combustion chamber gas temperature, means operably connecting said last mentioned means to said control element, stop means to limit adjustment of said control element, engine operating condition responsive means to adjustably position said stop means so as to limit the maximum adjustment of said control element to a predetermined safe value under the prevailing operating conditions, said condition responsive means including air intake temperature responsive means, combustion charnber exhaust gas temperature responsive means, and air intake pressure responsive means to control said stop means.

3. For use with an aircraft engine having a combustion chamber, an air intake conduit to said chamber, a fuel intake conduit to said chamber, an exhaust gas conduit from said chamber, means to control the supply of fuel to said combustion chamber, and combustion gas temperature responsive means to regulate the fuel supply control so as to maintain the combustion gases at a preselected temperature; a control mechanism comprising a manually operable control element, means to select the combustion chamber gas temperature, means operably connecting said last mentioned means to said control element, stop means to limit adjustment of said control element, engine operating condition responsive means to adjustably position said stop means so as to limit the maximum adjustment of said control element to a predetermined safe value under the prevailing operating conditions, said condition responsive means including a servomotor for adjustably positioning said stop means, and means for controlling said motor including air intake temperature responsive means, combustion chamber exhaust gas temperature responsive means, and air inlet pressure responsive means.

4. For use with an aircraft engine having a combustion chamber, an air intake conduit to said chamber, a fuel intake conduit to said chamber, an exhaust gas conduit from said chamber, means to control the supply of fuel to said combustion chamber, and combustion gas itemperature responsive means to regulate the fuel supply control so as to maintain the combustion gases at a preselected temperature; a control mechanism comprising a manually operable con-trol element, means to select the combustion chamber gas temperature; means `operably connecting said last mentioned means to said control element, stop means to limit adjustment of said control element, engine operating condition responsive means to adjustably position said stop means so as to limit the maximum adjustment of said control element to a predetermined safe value under the prevailing operating condi- Itions, lsaid condition responsive means including a computer mechanism for controlling said stop means, said last mentioned computer mechanism including air intake temperature and pressure responsive means, and exhaust gas temperature responsive means, rst control means operated by said pressure and air intake temperature responsive means to derive a signal to limit the selected combus-tion chamber temperature to a safe maximum combustion chamber temperature under the prevailing operating conditions, second control means operated by said pressure and air intake and exhaust gas temperature responsive means to derive a signal to limit the selected combustion chamber temperature to a value for effecting safe maximum engine power under the prevailing operating conditions, servomotor means for positioning said stop means, and signal selective means responsive .to the thus derived signals for operatively connecting 'to said servomotor means the control means effecting the lowest safe combustion chamber temperature so as to thereby effect -the positioning of said stop means in such a manner as to limit the maximum adjustment of the manual control element to a value for effecting both safe engine power and safe combustion chamber temperature under prevailing operating conditi-ons.

5. For use with an aircraft engine having a combustion chamber and adjustable means for varying the temperature of the combustion gases in said chamber; a computer mechanism comprising an electrical net work including a combustion chamber air intake temperature responsive means for effecting in said network a signal proportional Ito said temperature, an air intake pressure responsive means excited by said signal for effecting in said net work another signal proportional to the ratio of the air intake temperature to the air intake pressure, combustion chamber air intake and combustion chamber exhaust gas temperature responsive means for etfecting a signal measuring the difference between the air intake and exhaust gas temperatures and applied to said network in additive relation -to the last mentioned other signal to effect a resultant control signal, a servomotor controlled by the resultant signal, and means positioned by said servomotor for limiting adjustment of the temperature varying means to a temperature setting for eiecting maximum safe engine power under the air intake temperature and pressure and exhaust gas temperature conditions then prevailing.

6. For use with an aircraft engine having a combustion chamber and means for varying the temperature of the combustion gases in said chamber; a computer mechanism comprising an electrical network including a combustion chamber air intake temperature responsive means for effecting in said network a signal proportional to the ratio of unity to said temperature, an air intake pressure responsive means excited by said signal for effecting in said network another signal proportional to the ratio of the air intake pressure to the air intake temperature, combustion chamber air intake temperature responsive means for effecting a signal proportional to said air intake temperature and applied to said network in opposing relation to the last mentioned other signal to eect a resultant control signal, a servomotor controlled by the resultant signal, and means positioned by said servo- .22 motor for limiting the adjustment of fthe :,teniperatutii varying Imeans to a temperature setting `for effecting maximum safe combustion chamber temperature under the air .in-take temperature and pressure conditions then prevailing.

7. For use with an aircraft engine having a combustion chamber and means for varying the temperature of the combustion gases in said chamber; a computer mechanism comprising a 'first -electrical network including a combustion chamber air intake temperature responsive means for electing in said network a signal proportional to the ratio of unity to said temperature, an air intake pressure responsive means excited by said signal for effecting in said network another signal proportional to the ratio of the air intake pressure to the air intake temperature, combustion chamber air intake temperature responsive means for effecting a signal proportional to said air intake temperature and applied to said network in opposing relation to the last mentioned other signal to effect a resultant control signal, a second electrical network including a combustion chamber air intake temperature responsive means for effecting in said second network a signal proportional to said temperature, an air intake pressure responsive means excited by said signal for effecting in said second network another signal proportional to the ratio of the air intake temperature to the air intake pressure, combustion chamber air intake and combustion chamber exhaust gas temperature responsive means for eifecting a signal measuring the difference between the air intake and exhaust gas temperatures and applied to said second network in additive relation to the last mentioned other signal to effect a resultant control signal, a servomotor control signal selective means responsive to the difference between the resultant control signals of said iirst and second networks, said selective means operatively connecting one or the other of said networks to said servomotor in response to said diiferential signal, stop means positioned by said servomotor for limiting adjustment of the temperature varying means to a safe temperature setting, and said control signal selective means being arranged to operatively connect to said motor the control network having the lowest temperature setting control signal so as to cause said stop means to limit the temperature setting range of said temperature varying means to within the maximum safe combustion chamber temperature and engine power ranges under the air intake temperature and pressure and exhaust gas temperature conditions then prevailing.

8. An engine temperature selecting device, comprising in combination, a pilots control element, means for selecting engine temperature, means controlled by said engine temperature selecting means to regulate the engine temperature to the selected temperature value, means operatively connecting said control element to said temperature selecting means, stop means for limiting the adjustment of said temperature selecting means in a temperature increasing sense only, motor means for adjustably positioning said stop means, a computer mechanism for controlling said motor means so as to limit the range of selected engine temperatures to within a predetermined range of safe temperature values, and engine operating condition responsive means for affecting said computer mechanism so as to vary said safe range of selected temperature values with prevailing conditions.

9. An engine temperature selecting device, comprising in combination, a pilots control element, means for selecting engine temperatures during ight of the aircraft, a shaft operatively connecting said control element to said temperature selecting means, stop means rotatably mounted on said shaft, a dog rotatable by said shaft for engagement with said stop means to limit the adjustment of said temperature selecting means by said control element, motor means for adjustably positioning said stop 23 means, a computer mechanism for controlling said motor means so as to limit the selected engine temperature to Within a safe range, and engine operating condition responsive means for affecting said computer mechanism to vary said safe range with prevailing conditions.

References Cited in the file of this patent UNITED STATES PATENTS 2,160,194 Bates May 30, 1939 10 24 Fisehel Feb. 20, Martin et al. May 20, Orr Dec. 28, Orr Mar. 20, Orr, Jr. Mar. 20, Catford June 5, Bobier, Jr., et al June/19, Orr Aug. 14,

Kochenburger et al Mar. 17, 

